/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.catalina.realm;

import java.security.Principal;

import java.security.cert.X509Certificate;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

import javax.management.ObjectName;

import org.apache.catalina.Container;
import org.apache.catalina.Lifecycle;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.Realm;
import org.apache.catalina.util.StringManager;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;

/**
 * Realm implementation that contains one or more realms. Authentication is
 * attempted for each realm in the order they were configured. If any realm
 * authenticates the user then the authentication succeeds. When combining
 * realms usernames should be unique across all combined realms.
 */
public class CombinedRealm extends RealmBase {

	private static Log log = LogFactory.getLog(CombinedRealm.class);

	/**
	 * The string manager for this package.
	 */
	protected static StringManager sm = StringManager
			.getManager(Constants.Package);

	/**
	 * The list of Realms contained by this Realm.
	 */
	protected List<Realm> realms = new LinkedList<Realm>();

	/**
	 * Add a realm to the list of realms that will be used to authenticate
	 * users.
	 */
	public void addRealm(Realm theRealm) {
		realms.add(theRealm);

		if (log.isDebugEnabled()) {
			sm.getString("combinedRealm.addRealm", theRealm.getInfo(), Integer
					.toString(realms.size()));
		}
	}

	/**
	 * Return the set of Realms that this Realm is wrapping
	 */
	public ObjectName[] getRealms() {
		ObjectName[] result = new ObjectName[realms.size()];
		for (Realm realm : realms) {
			if (realm instanceof RealmBase) {
				result[realms.indexOf(realm)] = ((RealmBase) realm)
						.getObjectName();
			}
		}
		return result;
	}

	/**
	 * Return the Principal associated with the specified username and
	 * credentials, if there is one; otherwise return <code>null</code>.
	 * 
	 * @param username
	 *            Username of the Principal to look up
	 * @param credentials
	 *            Password or other credentials to use in authenticating this
	 *            username
	 */
	public Principal authenticate(String username, byte[] credentials) {
		Principal authenticatedUser = null;

		for (Realm realm : realms) {
			if (log.isDebugEnabled()) {
				log.debug(sm.getString("combinedRealm.authStart", username,
						realm.getInfo()));
			}

			authenticatedUser = realm.authenticate(username, credentials);

			if (authenticatedUser == null) {
				if (log.isDebugEnabled()) {
					log.debug(sm.getString("combinedRealm.authFail", username,
							realm.getInfo()));
				}
			} else {
				if (log.isDebugEnabled()) {
					log.debug(sm.getString("combinedRealm.authSucess",
							username, realm.getInfo()));
				}
				break;
			}
		}
		return authenticatedUser;
	}

	/**
	 * Return the Principal associated with the specified username, which
	 * matches the digest calculated using the given parameters using the method
	 * described in RFC 2069; otherwise return <code>null</code>.
	 * 
	 * @param username
	 *            Username of the Principal to look up
	 * @param clientDigest
	 *            Digest which has been submitted by the client
	 * @param nOnce
	 *            Unique (or supposedly unique) token which has been used for
	 *            this request
	 * @param realm
	 *            Realm name
	 * @param md5a2
	 *            Second MD5 digest used to calculate the digest : MD5(Method +
	 *            ":" + uri)
	 */
	public Principal authenticate(String username, String clientDigest,
			String once, String nc, String cnonce, String qop,
			String realmName, String md5a2) {
		Principal authenticatedUser = null;

		for (Realm realm : realms) {
			if (log.isDebugEnabled()) {
				log.debug(sm.getString("combinedRealm.authStart", username,
						realm.getInfo()));
			}

			authenticatedUser = realm.authenticate(username, clientDigest,
					once, nc, cnonce, qop, realmName, md5a2);

			if (authenticatedUser == null) {
				if (log.isDebugEnabled()) {
					log.debug(sm.getString("combinedRealm.authFail", username,
							realm.getInfo()));
				}
			} else {
				if (log.isDebugEnabled()) {
					log.debug(sm.getString("combinedRealm.authSucess",
							username, realm.getInfo()));
				}
				break;
			}
		}
		return authenticatedUser;
	}

	/**
	 * Return the Principal associated with the specified username and
	 * credentials, if there is one; otherwise return <code>null</code>.
	 * 
	 * @param username
	 *            Username of the Principal to look up
	 * @param credentials
	 *            Password or other credentials to use in authenticating this
	 *            username
	 */
	public Principal authenticate(String username, String credentials) {
		Principal authenticatedUser = null;

		for (Realm realm : realms) {
			if (log.isDebugEnabled()) {
				log.debug(sm.getString("combinedRealm.authStart", username,
						realm.getInfo()));
			}

			authenticatedUser = realm.authenticate(username, credentials);

			if (authenticatedUser == null) {
				if (log.isDebugEnabled()) {
					log.debug(sm.getString("combinedRealm.authFail", username,
							realm.getInfo()));
				}
			} else {
				if (log.isDebugEnabled()) {
					log.debug(sm.getString("combinedRealm.authSucess",
							username, realm.getInfo()));
				}
				break;
			}
		}
		return authenticatedUser;
	}

	/**
	 * Set the Container with which this Realm has been associated.
	 * 
	 * @param container
	 *            The associated Container
	 */
	public void setContainer(Container container) {
		for (Realm realm : realms) {
			// Set the realmPath for JMX naming
			if (realm instanceof RealmBase) {
				((RealmBase) realm).setRealmPath(getRealmPath() + "/realm"
						+ realms.indexOf(realm));
			}

			// Set the container for sub-realms. Mainly so logging works.
			realm.setContainer(container);
		}
		super.setContainer(container);
	}

	/**
	 * Prepare for the beginning of active use of the public methods of this
	 * component. This method should be called before any of the public methods
	 * of this component are utilized. It should also send a LifecycleEvent of
	 * type START_EVENT to any registered listeners.
	 * 
	 * @exception LifecycleException
	 *                if this component detects a fatal error that prevents this
	 *                component from being used
	 */
	public void start() throws LifecycleException {
		// Start 'sub-realms' then this one
		Iterator<Realm> iter = realms.iterator();

		while (iter.hasNext()) {
			Realm realm = iter.next();
			if (realm instanceof Lifecycle) {
				try {
					((Lifecycle) realm).start();
				} catch (LifecycleException e) {
					// If realm doesn't start can't authenticate against it
					iter.remove();
					log.error(sm.getString("combinedRealm.realmStartFail",
							realm.getInfo()), e);
				}
			}
		}
		super.start();
	}

	/**
	 * Gracefully terminate the active use of the public methods of this
	 * component. This method should be the last one called on a given instance
	 * of this component. It should also send a LifecycleEvent of type
	 * STOP_EVENT to any registered listeners.
	 * 
	 * @exception LifecycleException
	 *                if this component detects a fatal error that needs to be
	 *                reported
	 */
	public void stop() throws LifecycleException {
		// Stop this realm, then the sub-realms (reverse order to start)
		super.stop();
		for (Realm realm : realms) {
			if (realm instanceof Lifecycle) {
				((Lifecycle) realm).stop();
			}
		}
	}

	/**
	 * Return the Principal associated with the specified chain of X509 client
	 * certificates. If there is none, return <code>null</code>.
	 * 
	 * @param certs
	 *            Array of client certificates, with the first one in the array
	 *            being the certificate of the client itself.
	 */
	public Principal authenticate(X509Certificate[] certs) {
		Principal authenticatedUser = null;
		String username = null;
		if (certs != null && certs.length > 0) {
			username = certs[0].getSubjectDN().getName();
		}

		for (Realm realm : realms) {
			if (log.isDebugEnabled()) {
				log.debug(sm.getString("combinedRealm.authStart", username,
						realm.getInfo()));
			}

			authenticatedUser = realm.authenticate(certs);

			if (authenticatedUser == null) {
				if (log.isDebugEnabled()) {
					log.debug(sm.getString("combinedRealm.authFail", username,
							realm.getInfo()));
				}
			} else {
				if (log.isDebugEnabled()) {
					log.debug(sm.getString("combinedRealm.authSucess",
							username, realm.getInfo()));
				}
				break;
			}
		}
		return authenticatedUser;
	}

	@Override
	protected String getName() {
		// This method should never be called
		// Stack trace will show where this was called from
		UnsupportedOperationException uoe = new UnsupportedOperationException(
				sm.getString("combinedRealm.getName"));
		log.error(sm.getString("combinedRealm.unexpectedMethod"), uoe);
		throw uoe;
	}

	@Override
	protected String getPassword(String username) {
		// This method should never be called
		// Stack trace will show where this was called from
		UnsupportedOperationException uoe = new UnsupportedOperationException(
				sm.getString("combinedRealm.getPassword"));
		log.error(sm.getString("combinedRealm.unexpectedMethod"), uoe);
		throw uoe;
	}

	@Override
	protected Principal getPrincipal(String username) {
		// This method should never be called
		// Stack trace will show where this was called from
		UnsupportedOperationException uoe = new UnsupportedOperationException(
				sm.getString("combinedRealm.getPrincipal"));
		log.error(sm.getString("combinedRealm.unexpectedMethod"), uoe);
		throw uoe;
	}

}
